1. Field of the Invention
The present invention relates to a solenoid valve disposed, for example, over a fuel tank and incorporating a liquid surface detecting valve for detecting the liquid surface in the fuel tank.
2. Description of the Prior Art
A conventional solenoid valve incorporating a liquid surface detecting valve is, for example, disclosed in Japanese Patent Laid-Open Publication No. 62-53224 and illustrated in FIG. 2 which comprises a solenoid valve 33 disposed in parallel with and in the midway of an exhaust passage 32 for exhausting fuel evaporative emission at an upper stream of the solenoid valve 33 and at the upper portion in a fuel tank 30.
In the fuel tank 30 provided with the solenoid valve 33 having a liquid surface detecting valve 34, the liquid surface detecting valve 34 is usually located at the position corresponding to the liquid surface in the tank 30 and the solenoid valve 33 is closed. Accordingly, when fuel supplied first in the tank 30 (hereinafter referred to as first fuel) is consumed, the liquid surface detecting valve 34 is lowered in response to the liquid surface and fuel evaporative emission of the first fuel in the tank 30 reaches the solenoid valve 33.
In case of the supply of new fuel or a second fuel into the tank 30 (hereinafter referred to as second fuel) accompanied by the consumption and reduction of the first fuel in the tank 30, the solenoid valve 33 is open synchronously with the supply of the second fuel, hence, fuel evaporative emission of the first fuel is fed to a canister 31 via the solenoid valve 33, whereby a pressure in the tank 30 is reduced to thereby permit the second fuel to be supplied into the tank 30. Upon completion of the supply of the second fuel, fuel in the tank 30 reaches an upper level of the tank 30 and the liquid surface detecting valve is closed to thereby increase the pressure in the tank 30 whereby the supply of the second fuel is stopped. The solenoid valve 33 is closed synchronously with the stop of the supply of the second fuel.
Whereupon, fuel has generally a viscosity. Accordingly, adhesive force is generated in both the liquid surface detecting valve 34 exposed to fuel evaporative emission and the valve seat thereof. Due to the adhesive force, even if the liquid surface is lowered, the liquid surface detecting valve 34 is liable to be kept attached or adhered to the valve seat thereof and thus not lowered in the tank whereby the liquid surface detecting valve 34 does not effectively operate at the time of the supply of the second fuel.
On the other hand, there is a need for making the size of the solenoid valve 33 as small as possible although it is necessary to enlarge the exhaust passage adjacent to the solenoid valve 33 in order to exhaust fuel evaporative emission as quickly as possible in the fuel tank 30 at the time of the supply of the second fuel so that the second fuel can be smoothly supplied.